Continuous calibration of grade control system

ABSTRACT

A work machine includes a frame, a linkage assembly, a work implement connected to the linkage assembly, and a grade control calibration system. The grade control calibration system includes a vision processing system, which includes a sensor fixed to the linkage assembly and a first controller. The vision processing system is configured to measure a length of a cutting portion of the work implement, and to transmit the length of the cutting portion of the work implement. The grade control calibration system also includes a grade control system in communication with the vision processing system and the linkage assembly. The grade control system includes a second controller configured to receive the length of the cutting portion of the work implement from the first controller, and to calibrate a position of the work implement based on the received length of the cutting portion of the work implement.

TECHNICAL FIELD

The present disclosure relates generally to a grade control system, andmore particularly, to a method and system for continuous calibration ofthe grade control system of a work machine based.

BACKGROUND

Conventional earthmoving machines such as track-type tractors, motorgraders, scrapers, and/or backhoe loaders, may include a ground-engagingimplement, such as a dozer blade or bucket, which may be used on aworksite in order to alter a geography or terrain of a section of earth.The implement may be controlled by an operator and/or by an autonomousgrade control system. To achieve a final surface contour or a finalgrade, the implement may be adjusted to various positions by theoperator or the grade control system. Accurately positioning theimplement, however, requires knowledge by the grade control systemand/or operator of the machine as to the specific dimensions of theimplement and its components.

For example, the ground-engaging implements described above may includeearth cutting portions such as teeth, shrouds, and/or lips. These earthcutting portions may wear more quickly than underlying equipment, asthey initiate contact with the ground surface before the body of theexcavating bucket and may encounter highly abrasive materials. Theseconditions cause the earth cutting portions to erode and, eventually, towear out or fail. If not regularly updated, the grade control systemwill inaccurately position the implement during grading, resulting in anincorrect surface contour or grade. Manual calibration events aretypically performed at certain intervals, for example, monthly, tomeasure various components of the implement, including the earth cuttingportions, and to update the dimensions in the grade control system.However, manual calibration is tedious, time consuming, and costly foroperators and maintenance personnel.

Prior art attempts to determine wear associated with a part rely ondetermining when a part needs replacement. For example, U.S. 9,613,413describes systems and methods for determining part wear using a mobiledevice. The system relies on capturing digital images using a camera onthe mobile device and determining wear using a differential number ofpixels between the imaged part and a simulated surface of an unwornpart. A percentage or degree of wear is determined based on thesedistances. According to the degree of wear, an alert or warning isdisplayed to a user indicating replacement for the part is necessary.

In light of the foregoing, a need exists for continuous calibration ofgrade control systems.

SUMMARY

In accordance with one aspect of the present disclosure, a work machineis disclosed. The work machine may include a frame, a linkage assembly,a work implement connected to the linkage assembly, and a grade controlcalibration system. The grade control calibration system may include avision processing system, which may include a sensor fixed to thelinkage assembly and a first controller. The vision processing systemmay be configured to measure a length of a cutting portion of the workimplement, and to transmit the length of the cutting portion of the workimplement. The grade control calibration system may also include a gradecontrol system in communication with the vision processing system andthe linkage assembly. The grade control system may include a secondcontroller configured to receive the length of the cutting portion ofthe work implement from the first controller, and to calibrate aposition of the work implement based on the received length of thecutting portion of the work implement.

In accordance with another aspect of the present disclosure, a gradecontrol calibration system for a work machine is disclosed. The workmachine may include a frame, a linkage assembly and a work implement.The grade control calibration system may include a vision processingsystem and a grade control system. The vision processing system mayinclude an imaging device fixed to the linkage assembly and configuredto generate a three-dimensional point cloud of a cutting portion of thework implement, and a vision controller in electronic communication withthe imaging device and configured to calculate a current length of thecutting portion of the work implement based on the three-dimensionalpoint cloud generated by the imaging device. The vision controller maytransmit the current length of the cutting portion of the workimplement. The grade control system may be in communication with thevision processing system and the linkage assembly and may include agrading controller configured to receive the current length of thecutting portion of the work implement from the vision controller and tocalibrate a position of the work implement relative to the terrain basedon the received length of the cutting portion of the work implement.

In accordance with yet another aspect of the present disclosure, amethod of grading terrain using a work implement of a work machine. Thework machine may include a linkage assembly and a sensor coupled to thelinkage assembly. The method may include detecting the work implementwithin a field of view of the sensor; identifying, by the sensor, acutting portion of the work implement, calculating, by a controllerelectronically coupled to the sensor, a length of the cutting portion ofthe work implement; calibrating, by the controller, a grade controlsystem of the work machine based on the calculated length of the cuttingportion of the work implement; maneuvering, by the calibrated gradecontrol system, the cutting portion of the work implement proximate theterrain; and grading the terrain with the cutting portion of the workimplement.

These and other aspect and features of the present disclosure will bebetter understood upon reading the following detailed description whentaken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of an exemplary work machine, according to anembodiment of the present disclosure;

FIG. 2 is a schematic diagram of a grade control calibration system,according to an embodiment of the present disclosure;

FIG. 3 is a perspective view of a camera system of the exemplary workmachine of FIG. 1 , according to an embodiment of the presentdisclosure;

FIG. 4 is a front view of a work implement of the exemplary work machineof FIG. 1 , according to an embodiment of the present disclosure;

FIG. 5 is a perspective view of a work implement of the exemplary workmachine of FIG. 1 , according to an embodiment of the presentdisclosure; and

FIG. 6 is a flowchart illustrating a method of grading, according to anembodiment of the present disclosure.

DETAILED DESCRIPTION

Reference will now be made in detail to specific embodiments orfeatures, examples of which are illustrated in the accompanyingdrawings. Wherever possible, corresponding or similar reference numberswill be used throughout the drawings to refer to the same orcorresponding parts.

An exemplary embodiment of a work machine 10 is illustrated in FIG. 1 .The work machine 10 may be, for example, an excavator, a wheeled ortracked loader, a mining shovel, a backhoe loader, or any other type ofwork machine known in the art. As an excavator, the work machine 10 mayinclude a power source 12 (e.g., an engine, a motor, a battery bank,etc.) mounted to a frame 14 and configured to drive one or moreground-engaging elements 16 for propelling the work machine 10 across aworksite. The ground-engaging elements 16 may be mounted or movablycoupled to the frame 14 and may include, for example, tracks, wheels,and/or combinations thereof. The frame 14 may also support an operatorcab 18 configured to house, for example, an operator’s seat and anoperator console or other machine control devices for controllingvarious functions of the work machine 10. In other embodiments, however,the work machine 10 may be an autonomous machine, a semi-autonomousmachine, a remotely operated machine, or a remotely supervised machine,among others.

The illustrated work machine 10 may also include a linkage system 20 anda work implement 22 connected to the linkage system 20. The linkagesystem 20 may include a boom 24 pivotally connected to the frame 14, astick 26 pivotally connected to the boom 24, and a linkage 28 pivotallyconnecting the work implement 22 and the stick 26. The work implement 22may include a bucket 30 pivotally connected to the linkage 28. Thebucket 30 may include a cutting portion 32 which, as illustrated,comprises a plurality of teeth 34. In other embodiments, the cuttingportion 32 may comprise a smooth edge.

The work machine 10 may further include a sensor 40 configured to, amongother things, measure a length of each of the plurality of teeth 34. Byway of example only, and not by way of limitation, the sensor 40 may bean imaging device such as a smart camera or smart vision system, amonocular camera, an infrared camera, a high resolution camera, an arrayof one or more types of cameras, an opto-acoustic sensor, a radar, alaser based imaging sensor, or the like, or combinations thereof,configured to assist recognition, and monitoring of the work implement22 and the worksite. The sensor 40 may be positioned on the work machine10 to obtain a field of view 42 toward the work implement 22. Morespecifically, the sensor 40 may be an imaging device positioned on thework machine 10 to capture images in their field of view 42 duringoperation of the work machine, and having a dedicated processor onboard,including video processing acceleration provided by a field-programmablegate array (FPGA), a digital signal processor (DSP), a general purposegraphics processing unit (GP-GPU), or any other suitable microprocessorwith supporting application software, capable of determining depth andvolume from real-time images or videos.

As illustrated, the work machine 10 may include a left imaging device 40a mounted on a left side 44 of the boom 24, and a right imaging device40 b (not shown) mounted on the right side (not shown) of the boom. Inother embodiments, the work machine 10 may also include one or moreimaging devices 40 mounted on a left side of the stick 26 and/or a rightside of the stick. The imaging devices 40 a, 40 b may be stereo cameras.The left imaging device 40 a may continuously capture images and/orvideos in its field of view 42 a, which may include worksite terrainprimarily to the left side and in front of (in a direction of travel)the work machine 10 and at least a left half 46 (see also FIG. 4 ) ofthe work implement 22. The right imaging device 40 b may continuouslycapture images and/or videos in its field of view 42 b, which mayinclude worksite terrain primarily to the right side and in front of thework machine 10 and at least a right half 48 (see also FIG. 4 ) the workimplement 22.

Referring now to FIG. 2 , the work machine 10 may further include agrade control calibration system 100 including a vision processingsystem 200 and a grade control system 300. The vision processing system200 may include the left imaging device 40 a, the right imaging device40 b and a vision controller 202. The grade control system 300 mayinclude a plurality of position sensors 302, an inertial measurementunit (IMU) 304, a global positioning system (GPS) unit 306 and a gradecontroller 308. In one embodiment, the plurality of position sensors 302are electrohydraulic position sensors associated with hydrauliccomponents (e.g. cylinder or cylinder rods) of the boom 24, the stick 26and the work implement 22, and configured to detect positional and/orvelocity information associated with these components. Such linkagekinematics may be used to assist with calibrating a position of the workimplement 22, as will be discussed in further detail below.

The grade controller 308 may be in electronic communication with thevision controller 202, and both may communicate with a gatewaycontroller 50. The gateway controller 50 may, for example, provide aconnection between the vision controller 202 and the grade controller308 and at least one remote entity 52 via a network (not shown). In suchan arrangement, the gateway controller 50 may transmit data to andreceive data from the remote entity 52 via the network. The remoteentity 52 may include a web server, computing device and/or storagedevice (e.g. database). In one embodiment, the remote entity 52 may be adatabase for storing a variety of information related to the gradecontrol system 300 and the vision processing system 200. Morespecifically, the database may store a list of machines, including thework machine 10, each identified by a unique identifier. The table mayassociate each unique identifier with a set of data related to thecomponents of each machine. For example, as to the work machine 10, thetable may associate a set of characteristics associated with the workimplement 22, such as a bucket 30 identifier or model number, anoriginal number of teeth 34, an original number of lip shrouds 64 (FIG.4 ), an original length of each tooth, a 3D tooth profile, and a 3Dshroud profile. This data may be accessed and updated by both the visionprocessing system 200 and the grade control system 300 through thegateway controller 50.

Each of the vision controller 202, the grade controller 308 and thegateway controller 50 may include any type of device or any type ofcomponent that may interpret and/or execute information and/orinstructions stored within a memory (not shown) to perform one or morefunctions. The memory may include a random access memory (“RAM”), a readonly memory (“ROM”), and/or another type of dynamic or static storagedevice (e.g., a flash, magnetic, or optical memory) that storesinformation and/or instructions for use by the example components,including the information and/or instructions used by the visioncontroller 202, the grade controller 308 and the gateway controller 50(as explained in further detail below). Additionally, or alternatively,the memory may include non-transitory computer-readable medium ormemory, such as a disc drive, flash drive, optical memory, read-onlymemory (ROM), or the like. The memory may store the information and/orthe instructions in one or more data structures, such as one or moredatabases, tables, lists, trees, etc. Finally, each of the visioncontroller 202, the grade controller 308 and the gateway controller 50may include a processor (e.g., a central processing unit, a graphicsprocessing unit, an accelerated processing unit), a microprocessor,and/or any processing logic (e.g., an FPGA, an application-specificintegrated circuit (ASIC), etc.), and/or any other hardware and/orsoftware.

Referring now to FIG. 3 , the left imaging device 40 a is illustrated.While only the left imaging device 40 a is illustrated in FIG. 3 , thedescription and discussion herein of the left imaging device should beunderstood to refer analogously to the right imaging device 40 b, exceptwhere otherwise indicated or apparent. As illustrated, the left imagingdevice 40 a may be a stereo camera module including a pair of monochromelenses 53 and a color camera lens 54. The monochrome camera lens 53 maycapture, for each pixel of an image, an amount of light. In other words,the monochrome camera lens 53 may capture the image in black-and-white.Similarly, the color camera lens 54 may capture, for each pixel of animage, a color hue. In other words, the color camera lens 54 may capturethe image in color. The left imaging device 40 a may also be capable ofcapturing images of its field of view in all levels of ambient light(i.e. both during the day and at night) with or without color.

The left imaging device 40 a may be fixed to a mount 56, which may beinstalled on a portion of the boom 24 of the work machine 10. The mount56 may be magnetic, and may thus be repositionable on the boom 24, thestick 26, the frame 14 or another area of the work machine 10 in orderto adjust the field of view 42 a of the left imaging device 40 a. Inother embodiments, the mount 56 may be a mount typically known in theart which integrates the left imaging device 40 a on the work machine10.

The left imaging device 40 a utilizes a three-dimensional (3D) pointcloud system, in which points within an image captured by the leftimaging device (hereinafter referred to as a “stereo image”) arestitched together to generate a 3D cloud map from which the depth and/ordistance of objects with respect to the environment and to each othermay be determined. In operation, therefore, the left imaging device 40 amay capture a stereo image and generate a 3D cloud map of the worksite,the work implement 22, and any other objects within the left imagingdevice’s field of view 42 a. The vision controller 202 may use thestereo image to generate a disparity map, may overlay the 3D cloud maponto the disparity map, and consequently, measure relevant distances,depths, etc. More specifically, the vision processing system 200 maycalculate a length of a tooth 34 of the work implement 22 by generatinga 3D cloud map of the work implement 30, identifying the specific regionof the 3D cloud map that corresponds to the tooth 34 of the workimplement, generating a disparity map, and overlaying the tooth regionof the 3D cloud map on the disparity map to obtain a length value of thetooth.

As shown in FIGS. 4 and 5 , and as noted above, the work implement 22may comprise a bucket 30 with a cutting portion 32. The bucket 30 mayalso generally include a plurality of heel shrouds 58, a pair of sideprotectors 60, and a pair of side cutters 62. The cutting portion 32 mayinclude a plurality of ground engaging tool assemblies or teeth 34 and aplurality of lip shrouds 64. Each tooth 34 may include an adapter 66configured to engage a base edge 68 of the cutting portion 32 of thebucket 30. Each tooth 34 may also include a ground engaging tip 70removably attached to the adapter 66. The tip 70 may endure the majorityof the impact and abrasion caused by engagement with work material, andmay consequently wear down more quickly than, for example, the adapter66. As the grade control system 300 relies on knowing a length L of eachtooth 34 to determine a position of the work implement 22 relative tothe terrain of the work site, it is imperative that the grade controlsystem utilizes an accurate length of each tooth in its calibration.Traditionally, machine operators, owners, servicemen, or dealersperiodically observe the amount of erosion sustained or “wear level” ofeach tooth 34, measure each tooth, and manually update the measurementsassociated with the grade control system 300. However, this procedurecan be costly, time consuming and inaccurate.

INDUSTRIAL APPLICABILITY

The teachings of the present disclosure may find applicability in manyindustries including, but not limited to, earth moving equipment. Inaddition, the disclosed systems and methods may find application in anyenvironment in which determining a length of a part is desired. Thepresent solution reduces the time, energy and costs required tocontinually and manually measure a tooth of a work implement andcalibrate a grade control system, and enables an accurate position ofthe work implement while grading. One skilled in the art will recognize,however, that the disclosed grade control calibration system could beutilized in relation to other machine components subject to wearing anderosion that may or may not be associated with a work implement orground engaging tool.

Referring now to FIG. 6 , and with continued reference to FIGS. 1-5 , amethod 600 of grading using the present grade control calibration systemis provided in flowchart format. Prior to operation of the work machine10 at a worksite, a pre-existing three dimensional site map as well as awork tool profile may be retrieved by the work machine from the remoteentity 52. More specifically, an operator of the work machine 10 may usethe operator console in the operator cab to select the specific modelnumber of the bucket 30. The profile associated with the bucket 30 maythen be retrieved and loaded into the grade control system 300. As notedabove, the profile of the bucket 30 may include a bucket identifier ormodel number, an original number of teeth 34 installed on the bucket, anoriginal number of lip shrouds 64 installed on the bucket, an originallength of each tooth, a 3D tooth profile, and a 3D shroud profile.

As the work machine 10 operates, the sensors 40 may continuously scanthe work implement 22 and the environment around the work machine 10 asit moves about the worksite. To begin the calibration of the gradecontrol system, and to properly measure the length L of the teeth 34 ofthe work implement 22, the entire bucket 30 needs to be within thefields of view 42 a, 42 b of the left imaging device 40 a and the rightimaging device 40 b. As illustrated in FIG. 5 , for example, the bucket30 is within the fields of view 42 a, 42 b of the imaging devices 40,with an area of overlap 72. To achieve this alignment, the grade controlsystem 300 and the vision processing system 200 monitor the linkagekinematics of the work machine 10. Namely, data transmitted to the gradecontroller 308 from the plurality of position sensors 302, as well asdata provided by the IMU 304, and global positioning data provided bythe GPS unit 306 is monitored until the values of each linkage kinematicdata enters a predetermined threshold (step 602).

Once the threshold values are met, the bucket 30 is considered alignedwithin the fields of view 42 a, 42 b of the left and right imagingdevices 40 a, 40 b, and the imaging devices 40 may begin their detectionprocess (step 604). For example, the left imaging device 40 a wouldcapture a stereo image of the bucket 30, as illustrated in FIG. 5 , forexample, and transmit the image to the vision processing controller 202(step 606). Simultaneously, the right imaging device 40 b would capturea stereo image of the bucket 30, as illustrated in FIG. 5 , for example,and transmit the image to the vision processing controller 202 (step606). The vision controller 202 may use the stereo images to generate adepth or disparity map.

Once received by the vision processing controller 202, the images areanalyzed and the plurality of teeth 34, the plurality of lip shrouds 64and other implements (e.g. side cutters 62) may be identified usingmachine learning algorithms, as generally understood in the art. Themachine learning algorithms may be trained to detect positions of teeth34, lip shrouds 64, and other implements and to generate a 3D pointcloud outline of the teeth, shroud and other detected implements (step606).

At a step 608, the orientation of the teeth 34, lip shrouds 64 and otherimplements are verified with the profile data associated with the modelof the bucket 30. For example, if the machine learning algorithmsidentify only two teeth 34, but the bucket profile indicates thisparticular model of bucket 30 should have four teeth, then a discrepancyis noted. More specifically, at step 610, to record any discrepancies, anon-detection counter is incremented and stored on the remote entity 52.Once the non-detection counter exceeds a pre-determined threshold, analert is generated and displayed to the operator of the work machine 10indicating that the respective non-detected teeth 34, lip shrouds 64and/or other implement are missing.

At a step 612, the vision processing controller 202 may superimpose each3D point cloud generated for detected teeth 34, lip shrouds 64 and otherimplements over the previously generated disparity map. Then, withrespect to each tooth 34 and lip shroud 64 specifically, the length L ofeach detected tooth and the length of each detected lip shroud iscalculated from the 3D point clouds as measured inside the boundaryoutlined by the machine learning algorithms (step 613). The measuredlength L of each tooth 34 is transmitted from the vision processingcontroller 202 to the grade controller 308, which updates the currentvalue of length L of each tooth 34 in the bucket 30 profile within thegrade control system 300 (step 613).

Finally, the grade control system 300 utilizes the updated length Lvalue of each tooth 34 in its configuration and positioning of thebucket 30 within the worksite. More specifically, the grade controlsystem 300 utilizes the 3D site map and the bucket 30 profile data toaccurately position the work implement 22. With inaccurate toothmeasurements, the grade control system 300 may believe a grade is deeperor shallower than its actual depth. This is important, for example, whenwater or gas pipes are present in the ground. As such, at step 614, thegrade control system 300 utilizes the updated current value of thelength L of each tooth 34 to accurately position the work implement 22within the terrain of the worksite, and according to defined boundariesof the 3D site plan.

While aspects of the present disclosure have been particularly shown anddescribed with reference to the embodiments above, it will be understoodby those skilled in the art that various additional embodiments may becontemplated by the modification of the disclosed machines, systems andassemblies without departing from the scope of what is disclosed. Suchembodiments should be understood to fall within the scope of the presentdisclosure as determined based upon the claims and any equivalentsthereof.

What is claimed is:
 1. A work machine, comprising: a frame; a linkageassembly; a work implement connected to the linkage assembly; and agrade control calibration system including: a vision processing systemincluding a sensor fixed to the linkage assembly and a first controller,the vision processing system configured to measure a length of a cuttingportion of the work implement and to transmit the length of the cuttingportion of the work implement, and a grade control system incommunication with the vision processing system and the linkageassembly, the grade control system including a second controllerconfigured to receive the length of the cutting portion of the workimplement from the first controller and to calibrate a position of thework implement based on the received length of the cutting portion ofthe work implement.
 2. The work machine of claim 1, wherein the linkageassembly includes a boom pivotally connected to the frame and a stickpivotally connected to the boom and the work implement.
 3. The workmachine of claim 1, wherein the work implement is a bucket including aplurality of teeth.
 4. The work machine of claim 3, wherein the cuttingportion of the work implement corresponds to the plurality of teeth andthe sensor is configured to measure the length of each of the pluralityof teeth.
 5. The work machine of claim 3, wherein the work implement isa bucket including a smooth cutting edge, the smooth cutting edgeextending a width of the bucket.
 6. The work machine of claim 5, whereinthe cutting portion of the work implement corresponds to the smoothcutting edge and the sensor is configured to measure the length of thesmooth cutting edge along the width of the bucket.
 7. The work machineof claim 1, wherein the sensor is a stereo camera that generates athree-dimensional point cloud of the cutting portion of the workimplement.
 8. The work machine of claim 7, wherein the stereo cameraincludes a monochrome lens and a color lens.
 9. A grade controlcalibration system for a work machine including a frame, a linkageassembly and a work implement, the grade control calibration system,including: a vision processing system, including: an imaging devicefixed to the linkage assembly and configured to generate athree-dimensional point cloud of a cutting portion of the workimplement, and a vision controller in electronic communication with theimaging device and configured to calculate a current length of thecutting portion of the work implement based on the three-dimensionalpoint cloud generated by the imaging device, the vision controllerfurther configured to transmit the current length of the cutting portionof the work implement; and a grade control system in communication withthe vision processing system and the linkage assembly, the grade controlsystem including: a grading controller configured to receive the currentlength of the cutting portion of the work implement from the visioncontroller and to calibrate a position of the work implement relative toa terrain based on the received current length of the cutting portion ofthe work implement.
 10. The grade control calibration system of claim 9,wherein the linkage assembly includes a boom, a stick and a plurality ofelectrohydraulic position sensors configured to transmit kinematics datato the vision controller.
 11. The grade control calibration system ofclaim 10, wherein the vision controller determines whether the workimplement is within a field of view of the imaging device using thekinematics data.
 12. The grade control calibration system of claim 9,wherein the grade control system includes a memory module for storing athree-dimensional site map and a work tool profile, the work toolprofile including an original length of the cutting portion of the workimplement and a last measured length of the cutting portion of the workimplement.
 13. The grade control calibration system of claim 12, whereinthe grading controller updates the last measured length of the cuttingportion of the work implement to the current length of the cuttingportion of the work implement in the memory module.
 14. The gradecontrol calibration system of claim 13, wherein the grading controllercalibrates the grade control system using the site map and the updatedlast measured length of the cutting portion of the work implement.
 15. Amethod of grading terrain using a work implement of a work machine, thework machine including a linkage assembly and a sensor coupled to thelinkage assembly, the method comprising: detecting the work implementwithin a field of view of the sensor; identifying, by the sensor, acutting portion of the work implement; calculating, by a controllerelectronically coupled to the sensor, a length of the cutting portion ofthe work implement; calibrating, by the controller, a grade controlsystem of the work machine based on the calculated length of the cuttingportion of the work implement; maneuvering, by the calibrated gradecontrol system, the cutting portion of the work implement proximate theterrain; and grading the terrain with the cutting portion of the workimplement.
 16. The method of claim 15, wherein the work implement is abucket, and the cutting portion of the work implement is a plurality ofteeth.
 17. The method of claim 16, wherein the calculating furtherincludes calculating, by the controller, the length of each of theplurality of teeth.
 18. The method of claim 15, wherein the identifyingfurther includes: generating, by the sensor, a current three-dimensionalpoint cloud scan of the cutting portion of the work implement.
 19. Themethod of claim 18, wherein the calculating further includes:retrieving, by the controller, a previous three-dimensional point cloudscan of the cutting portion of the work implement, and generating, bythe controller, a disparity map of the cutting portion of the workimplement based on the previous three-dimensional point cloud scan andthe current three-dimensional point cloud scan.
 20. The method of claim19, wherein the calculating the length of the cutting portion of thework implement is based on the generated disparity map.